1. Field of the Invention
The present invention relates, in general, to control systems in internal combustion engines and, specifically, to the identification of a traffic pattern in which a vehicle is traveling for input into the vehicle control systems.
2. Description of the Art
A vehicle contains many control systems. The driving environment to which the vehicle is exposed affects the operation of many of these systems. In particular, the determination of following distance, resume rates, etc., in a radar cruise control system could benefit from knowing whether the vehicle is traveling in city, suburban, or highway traffic. Similarly, the type of traffic in which a vehicle is traveling could be used to vary the damping rate of shock absorbers to obtain the desired road xe2x80x9cfeelxe2x80x9d in ride control systems.
Nothing in the vehicle controller currently takes traffic pattern into account.
The present invention is a method of and apparatus for determining the traffic pattern in which a vehicle is traveling as city, suburban or highway traffic. The method comprises the steps of sampling a speed of the vehicle at predetermined sampling intervals; establishing a prediction period; performing the sampling step until the end of the prediction period is reached; determining an average speed and a speed variation of the vehicle upon reaching the prediction period; and determining the traffic pattern using the average speed and the speed variation, preferably by using a lookup table.
The apparatus of the present invention comprises means for sampling a speed of the vehicle at predetermined sampling intervals; means for establishing a prediction period; means for performing the sampling step until the prediction period is reached; means for determining an average speed and a speed variation of the vehicle upon reaching the prediction period; and means for determining the traffic pattern using the average speed and the speed variation, preferably a lookup table.
The prediction period is a variable length of time over which sampling occurs. In a preferred aspect of the invention, the prediction period is the shorter of a time interval or the amount of time it takes to travel a distance interval. The prediction period thus varies as a function of distance traveled, and the prediction period is limited for conditions where the distance interval is not reached within the time interval. Therefore, the determination of the traffic pattern takes place quicker at higher speeds.
Adjustment of the prediction period can be used to quickly recognize transitions from one traffic pattern to another. In one aspect of the invention, this is done by comparing the average speed during the prediction period to a minimum speed when the traffic pattern is highway traffic and adjusting the distance interval by a first modifier based on the results of the comparing step. Specifically, if the average speed is less than the minimum speed, a transition from highway traffic is indicated. The modifier is used to reduce the time to the next prediction of the traffic pattern.
In another aspect of the invention, adjustment of the prediction period to quickly recognize transitions from one traffic pattern to another is done by comparing the average speed during the prediction period to a maximum speed when the traffic pattern is city traffic and adjusting the distance interval by a second modifier based on the results of the comparing step. Specifically, if the average speed is greater than the maximum speed, a transition from city traffic is indicated. The modifier is used to reduce the time to the next prediction of the traffic pattern.
The present invention, by identifying the traffic pattern type as city, suburban or highway, allows customization of the performance of a variety of powertrain control systems system based on traffic conditions. In cruise control systems, for example, the proportional gain and/or the integral gain used in the speed control algorithm will be a function of the traffic pattern. In addition, different gains for torque and/or braking control will be available for different traffic patterns. The method of the present invention is easy to calibrate and requires no additional hardware in order to function.